Inductive voltage generator

ABSTRACT

A voltage generator ( 1 ) for conversion of non-electrical primary energy (PE) to a voltage signal (USIG, USIG′) by means of induction. The voltage generator ( 1 ) has at least one mechanical energy store ( 2 ) for holding the primary energy (PE), and which has at least one changeover point (P). At least one induction system ( 3 ) is provided which can be coupled to the mechanical energy store ( 2 ), with the mechanical energy store ( 2 ) carrying out a movement on reaching the at least one changeover point (P) by means of which movement a voltage signal (USIG, USIG′) can be induced in the induction system ( 3 ).

The invention relates to an inductive voltage generator for conversionof non-electrical primary energy to a voltage signal by means ofinduction, which is suitable in particular for sensors and signalingsystems without batteries, to a switch, to a sensor system and to amethod for voltage generation based on the induction principle.

WO 98/36395 discloses an arrangement for generation of codedradio-frequency signals, in which a transducer for conversion ofnon-electrical primary energy to low-frequency electrical energy isprovided, inter alia by means of electrodynamic conversion ofoscillation/acceleration change energy. A spring which can be movedbeyond a dead point and which acts suddenly on the transducer whenloaded beyond the dead point, for generating a piezo-voltage isdescribed.

Until now, a voltage generator having a piezoelectric element and asmall dynamo has essentially been known for inductive conversion ofmechanical primary energy. The dynamo solution comprises an arrangementwith an induction coil having an iron core and a permanent magnet whichoscillates in front of the iron core; this arrangement is comparativelycomplex and has a comparatively large volume.

The object of the present invention is to provide a compact capabilityfor high-efficiency inductive voltage generation, and which isparticularly suitable for sensors and signaling systems withoutbatteries.

This object is achieved by means of a voltage generator as claimed inclaim 1, by a switch as claimed in claim 4, by a sensor system asclaimed in claim 5, and by a method as claimed in claim 6. Advantageousrefinements can be found in the dependent claims.

For this purpose, the voltage generator has at least one mechanicalenergy store for holding the non-electrical primary energy, and at leastone induction system which can be coupled to it.

The primary energy may, for example, be mechanical process energy (forexample (finger) pressure, tension or vibration) and/or environmentalenergy (for example a temperature difference), or a combination of both.The mechanical process energy may, for example, be provided by a manualoperation, for example of a switch. The thermal environmental energymay, for example, be introduced into the mechanical energy store via anelement with a temperature-dependent expansion behavior, for example abimetallic switch or a so-called memory element.

The mechanical energy store is any system which can store energyessentially reversibly by changing mechanical characteristic variables(for example pressure, tension, potential energy, deformation etc.). Forexample, a spring (tension spring, bending element, etc.) can storeexpansion energy or a weight can store potential energy and, forexample, can emit it again via the movement of a plunger. A pneumaticspring, which can emit pressure energy via a plunger, may, for example,also be regarded as a mechanical energy store.

The induction system is designed such that it is suitable for emittingan induction voltage, and typically has at least one induction coil,possibly with a magnetic core, which generally contains iron.

The induction system is coupled to the mechanical energy store such thatthe induction voltage can be induced by a movement of the mechanicalenergy store in the induction system; the mechanical energy that isemitted is thus converted to a voltage signal, by means of inductionfrom the induction system. By way of example, the mechanical energystore for this purpose contains a magnet, preferably a permanent magnet,which, after reaching the changeover point, is moved by the mechanicalenergy that is released such that it causes a change over time in themagnetic flux Φ in the area of the induction system. The mechanicalenergy store may thus also be used as a transformer for non-mechanicalprimary energy to mechanical motion energy.

The voltage generator has at least one changeover point, on reachingwhich at least some of the mechanically stored energy is converted intomovement for inductive generation of the voltage signal. The changeoverpoint thus analogously corresponds to a threshold value of the storedmechanical energy. Before reaching the changeover point, the primaryenergy which is supplied to the mechanical energy store is essentiallyonly stored in it.

The changeover point may be dependent on the environment and on theinduction system. It is advantageous for there to be more than onechangeover point and/or for it to be possible to reach the respectivechangeover point from both sides, because this makes it possible toadjust the voltage generation in a flexible manner. It is alsoadvantageous for the movement to take place as suddenly as possible. Forexample, when using a spring as the energy store, the changeover pointcan be reached both by means of a pressure load and by means of atension load, in which case the level of the changeover point may differin the two operating directions.

The use of the mechanical energy store with a changeover point resultsin the advantage that the profile of the magnetic field change, andhence of the induction voltage, does not depend on the time effect ofthe primary energy. Furthermore, the magnitude of the converted energyis essentially constant.

It is preferable for the primary energy to be supplied to the mechanicalenergy store by means of a control element, for example a switch. Thecontrol element may also be part of the mechanical energy store.

The voltage generator is illustrated schematically in more detail in thefollowing exemplary embodiments.

FIG. 1 shows the principle of voltage generation,

FIG. 2 shows a sensor system which contains the inductive voltagegenerator for energy supply,

FIG. 3 shows various positions during operation of the voltagegenerator.

FIG. 1 shows an outline circuit diagram for voltage generation.

Non-electrical primary energy PE which is available from the environment(for example a temperature difference AT) or from a process (for examplefinger pressure) is fed into the mechanical energy store 2 as part ofthe voltage generator 1. After reaching the changeover point P, itsmechanical energy is introduced via a movement into the induction system3, which is likewise a part of the voltage generator 1, where it is usedto generate a voltage signal USIG. The voltage signal USIG is thenavailable to a load, in this case, a transmitter 4 with a sensor 5connected to it. The voltage generator is particularly suitable forloads without batteries, for example click sensors and radioremote-control switches. The transmitter 4 may, for example, be a radioremote-control switch, and may transmit transmission messages by radioIR etc.

FIG. 2 shows a side view of one preferred embodiment of a voltagegenerator 1.

A spring 6 (which may also be preloaded) is used as the mechanicalenergy store 2 in this figure.

The right-hand end of the spring 6 is attached to a permanent magnet 7.In this position, the permanent magnet 7 rests on an iron core 9 whichis surrounded by an induction coil 8; the induction coil 8 and iron core9 are part of the induction system 3. Instead of the mechanical tensionspring 6, a rotary spring, a weight or a pneumatic spring may also beused, for example, as the mechanical energy store 2.

A load in the form of a transmitter 4, which comprises a sensor 5 and aradio-frequency transmission stage, is connected to the induction coil 8via an electrical connection 10.

The left-hand end of the spring 6 is connected to an operating unit foroperation of the spring 6 (not illustrated here), for example to one endof a rocker switch.

The figure elements a) to d) of FIG. 3 show an operating and resettingprocess for the apparatus shown in FIG. 2.

The left-hand end of the spring 6 in FIG. 3 a is loaded in the directionof the arrow. As the tensile stress increases, more mechanical energy isstored in the spring 6. In this figure, the stress in the spring 6 isnot yet sufficient to release the magnetic adhesion of the permanentmagnet 7 from the iron core 9.

In FIG. 3 b, the tensile stress in the spring 6 has become sufficient torelease the permanent magnet 7 from the iron core 9. The movement of thepermanent magnet 7 produces a change over time in the magnetic flux Φ,as a result of which a voltage UISG is induced in the induction coil 8;the mechanically stored energy is thus converted to electrical energy.

The changeover point (“mechanical dead point”), at which separationtakes place, is dependent only on the stress in the spring 6. Thechangeover point is advantageously also defined, for example, by thestrength of the magnetic field itself.

In FIG. 3 c, the spring 6 is now operated in the opposite direction. Thespeed at which the permanent magnet 7 approaches the iron core 9 isgoverned by the operating process and by the attraction force betweenthe permanent magnet 7 and the iron core 9. As the interaction forceincreases, the speed of the permanent magnet 6 also increases. Itsmovement in the opposite direction likewise induces a voltage signalUSIG′ in the induction coil. The movement direction of the mechanicalenergy store 2 can advantageously be determined in the load, for exampleby detection of the polarity of the voltage signals USIG, USIG′. It isthus possible to distinguish for example whether a switch is beingswitched on or being switched off.

FIG. 3 d shows the arrangement in the rest position after returning tothe initial position.

In the present exemplary embodiment, the permanent magnet 7 thus has twodefined limit positions in which it is held in a stable state. Under theinfluence of the primary energy, the spring 6 stores mechanical energyuntil, on reaching at least one changeover point, the permanent magnet 7snaps open to its other stable limit position, with the mechanicalenergy from the spring 6 being converted at least partially into thevoltage signal USIG, USIG′.

This voltage generator may be physically very compact, operates withrelatively high efficiency, is simple to manufacture and furthermore hasthe advantage of a mechanically defined switching point. Only a simplesnap-action movement is required instead of a complex oscillating magnetmovement.

The invention also relates to switches and sensor systems which have thevoltage generator, for example click sensors, light switches etc., inparticular switches and sensor systems without batteries, which cantransmit and receive messages by radio. As exemplary embodiments for thevoltage generator, reference should be made to WO 98/36395, inparticular to the use of switches and sensors in a powerlinecommunication (PLC) system, see, for example, Süddeutsche Zeitung [SouthGerman Daily Newspaper], No. 74 dated Mar. 29, 2001, page 27. Thevoltage generator is, of course, not restricted to these exemplaryembodiments.

1. A voltage generator (1) for conversion of non-electrical primaryenergy (PE) to a voltage signal (USIG, USIG′) by means of induction,characterized in that the voltage generator (1) has at least onemechanical energy store (2) for holding the primary energy (PE), andwhich has at least one changeover point (P), at least one inductionsystem (3) which can be coupled to the mechanical energy store (2), withthe mechanical energy store (2) carrying out a movement on reaching theat least one changeover point (P) by means of which movement a voltagesignal (USIG, USIG′) can be induced in the induction system (3).
 2. Thevoltage generator (1) as claimed in claim 1, in which the mechanicalenergy store (2) contains a spring (6) to which a magnet, in particulara permanent magnet (7) is attached.
 3. The voltage generator (1) asclaimed in claim 2, in which the induction system (3) has an inductioncoil (8) with a ferromagnetic core (9), in which the magnet can beplaced on the ferroelectric core.
 4. A switch, in particular formechanical operation, having a voltage generator (1) as claimed inclaim
 1. 5. A sensor system, having a voltage generator (1) as claimedin claim 1, and having at least one sensor (5).
 6. A method forinductive voltage generation, in which primary energy (PE) is stored ina mechanical energy store (2) until at least one changeover point (P) isreached, the mechanical energy store (2) is moved on reaching thechangeover point (P) such that a voltage signal (USIG, USIG′) isgenerated in an induction system (3) which is coupled to the mechanicalenergy store (2).
 7. The method as claimed in claim 6, in which theprimary energy (PE) is stored in the mechanical energy store (2) byexpansion or deformation of said mechanical energy store (2).
 8. Themethod as claimed in claim 6, in which, on reaching the changeover point(P), a magnet, in particular a permanent magnet (7), is moved such thatan induction voltage (USIG, USIG′) is generated by means of a change ina magnetic flux (Φ) in the area of an induction coil (8).